JP2005262779A - Phase variation type optical information recording medium - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a phase variation type optical information recording medium which has excellent recording characteristics in a blue wavelength (405 nm). <P>SOLUTION: This phase variation type optical information recording medium is constituted by laminating at least a lower dielectric layer, a recording layer, an upper dielectric layer, a sulfuration-resistant barrier layer, and a reflective layer on a base board in this order. The recording layer contains In<SB>α</SB>Te<SB>β</SB>(in this case, α and β represent a composition ratio (atomic %), 43.5≤β≤64 is satisfied, and also, α+β=100 is satisfied.), and the film thickness of the recording layer is 4 to 20 nm. On the base board, at least a first recording layer and a second recording layer are laminated in this order. The first recording layer which is located on the front surface in the laser irradiation direction contains In<SB>α</SB>Te<SB>β</SB>(in this case, α and β represent a composition ratio (atomic %), 43.5≤β≤64 is satisfied, and also, α+β=100 is satisfied.), and the film thickness of the first recording layer is 4 to 12 nm. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

The present invention relates to a phase change optical information recording medium (hereinafter sometimes referred to as “optical information recording medium”).
In particular, the present invention relates to a phase change optical information recording medium having excellent recording characteristics at a blue wavelength (405 nm).

  Conventionally, optical discs such as CD-R, CD-RW, etc., output sound, text, or image signals along a circumferential direction on a plastics circular substrate such as polycarbonate or a recording layer provided thereon. The recording layer is used, and a reflective layer is formed by depositing or sputtering a metal such as aluminum, gold or silver on the surface. In this case, laser light is incident from the substrate surface side of the optical disc, and signal recording and reproduction are performed.

  On the other hand, since the amount of information handled by computer memory, image and audio file memory, optical cards, etc. has increased significantly, the signal recording capacity and signal information of optical discs such as DVD + RW, DVD-RW, and DVD-RAM have increased. Densification is progressing. Currently, the recording capacity of a CD is about 650 MB, and the capacity of a DVD is about 4.7 GB. However, a higher recording density is required.

  As a method for increasing the recording density, it has been studied to shorten the wavelength of the light source in the optical system and increase the numerical aperture (NA) of the objective lens. However, it is difficult to improve the recording density only by two-dimensional recording. It has become to. In view of this, a method for accumulating information records by multilayering recording layers in the thickness direction of the recording medium has been studied.

As such a multilayering method, for example, there is a technique described in Patent Document 1 or the like. However, in this example, although the concept of multi-layering is described, since the specific contents regarding the recording medium are not described, the implementation method is unknown. On the other hand, a multilayer recording method in which a phase change recording layer is provided in the light incident direction has been proposed (see Patent Document 2 and Patent Document 3). Each of them has a recording layer having a structure in which the layer structure is two layers, the layer through which light is transmitted first is Sb ₂ Se ₃ , and the other layer is composed of a Ge ₂ Sb ₂ Te ₅ composition. In the case of this recording layer, there is a problem that when performing high-speed recording, the recording sensitivity is deteriorated and high-density recording is difficult.

  For example, when the recording layer has a multilayer structure with the two-layer structure, the film thickness of the first recording layer on the light incident side is used to improve the light irradiation to the second recording layer or improve the transmission of reflected light. As a result, the light transmission increases, but the film thickness becomes non-uniform, or a large power laser output is required in the crystallization process (initialization process). Further, there are technically difficult problems such as difficulty in obtaining a recording signal difference.

On the other hand, as a recording material suitable for high-speed recording, _(here, it refers to a material having a composition of Sb _{60 to 85 Te 15 to 40)} the material of SbTe system having a composition of eutectic near the main component, an upper dielectric A rapid cooling type structure in which the body layer has a thin structure of about 20 nm or less has been proposed (see, for example, Patent Document 4 and Patent Document 5).

However, even if the phase change material which is said to be suitable for high-speed recording is a material preferable for the red wavelength, an excellent recording signal difference cannot be obtained for the blue wavelength. Specifically, FIG. 3 shows changes in optical characteristics depending on the wavelength of SbTe having a composition in the vicinity of a normal eutectic system (Sb ₇₅ Te ₂₅ ). Here, in FIG. 3, the display of amorphous n and amorphous k assumes an amorphous mark that has become amorphous by heating to a molten state by laser irradiation and then rapidly cooling, and its optical constant n and extinction coefficient. The value of k is shown. The vertical axis indicating the value of the optical constant n is on the left side, and the vertical axis indicating the value of the extinction coefficient k is on the right axis. The values on FIG. 3 plot the measured values after deposition of the phase change recording material in an amorphous state. The indications of the crystal n and the crystal k indicate the values of the optical constant n and the extinction coefficient k of the phase change recording film that has been crystallized by heating to a molten state by laser irradiation and then gradually cooling. Actually, the membrane surface is initialized by the initialization device, and the measured values are plotted. For both the optical constant n and the extinction coefficient k, the amorphous state is indicated by a thick line, and the crystalline state is indicated by a thin line. Moreover, the arrow has shown the width | variety of the change from an amorphous state in a blue wavelength (405 nm) to a crystalline state. The larger the change width, the larger the signal difference between the unrecorded state and the recorded state. The optical constant difference of the material near the eutectic composition at the blue wavelength is Δn = 1.40 and Δk = 0.256.

  In general, the optical constants at the red wavelength (λ = 660 nm) of the SbTe phase change material having a composition near the normal eutectic system are n≈4.2 to 4.3, k≈2.45 to 2.2. About 65. When this same phase change material is evaluated at a blue wavelength (λ = 405 nm), the optical constants of most materials are in an amorphous state, and n≈2.5 to 2.6, k≈2.9 to It becomes about 3.0. As described above, the normal SbTe phase change material has a small absolute value of the optical constant n at a blue wavelength, and thus it is difficult to recognize the change in the optical constant as a signal difference. As a result, it is difficult to obtain the signal amplitude. Therefore, in order to perform high-speed recording at the blue wavelength, it is necessary to select a material having a large optical constant n even at the blue wavelength.

  In the case of an information recording medium comprising a multilayer recording layer, light transmission / light absorption of the recording layer becomes a problem. In particular, a high transmittance is required for the first recording layer on which light is first incident. This is because if the transmittance of the first recording layer located in front of the laser irradiation direction is not high, it becomes difficult to record on the recording layer on the far side. Therefore, the first recording layer is advantageous in terms of transmittance when the extinction coefficient k of the optical constant is small. From this point of view, a material having a large absolute value of the refractive index n at a blue wavelength and a small extinction coefficient k is optimal as the material of the first recording layer.

  Furthermore, it has been found from research by the present inventors that in order to form a first recording layer with high transmittance, it is not necessary to simply reduce the film thickness. That is, as a result of the experiment, when the first recording layer having a thin film thickness is formed, the transition linear velocity changes. In the case of a single recording layer, the linear velocity is obtained when the recorded condition is applied to the multilayer first recording layer. It was found that problems such as unable to record would occur unless the change was made. Therefore, the first recording layer material for the blue multilayer is required to be a material having a large absolute value of the refractive index n at a blue wavelength, a small extinction coefficient k, and a fast transition linear velocity. At present, there is a need for further improvements and developments.

JP-A-8-287474 Japanese Patent Laid-Open No. 9-198709 Japanese Patent Laid-Open No. 11-195243 JP 2000-233576 A Japanese Patent No. 3235503

  This invention is made | formed in view of this present condition, and makes it a subject to solve the said various problems in the past and to achieve the following objectives. That is, the present invention can obtain the reflectance difference of the mark recorded at the blue wavelength, can obtain excellent optical characteristics even at the blue wavelength, can have a high recording density, and can perform high-speed recording. Another object of the present invention is to provide a high-performance phase change optical information recording medium in which the recording sensitivity does not decrease.

  In order to solve the above-mentioned problems, the present inventors have made extensive studies and as a result, obtained the following knowledge. That is, it has been found that an InTe-based material has been discovered as a recording layer material capable of obtaining excellent optical characteristics even at a blue wavelength, and that a storage life can be extended by using a GeTe-based material together.

The present invention is based on the above findings of the present inventors, and means for solving the above problems are as follows. That is,
<1> On the substrate, at least a lower dielectric layer, a recording layer, an upper dielectric layer, a sulfide-resistant barrier layer, and a reflective layer are laminated in this order, and the recording layer is In _α Te _β (where α, β represents a composition ratio (atomic%), 43.5 ≦ β ≦ 64, and α + β = 100), and the thickness of the recording layer is 4 to 20 nm. It is a phase change optical information recording medium. In the phase change type optical information recording medium of the present invention, since the recording layer is made of an alloy containing at least In and Te as main components, a difference in reflectance between marks recorded at a blue wavelength can be obtained. Also excellent optical characteristics can be obtained.

<2> The phase change optical information recording medium according to <1>, wherein the recording layer contains at least one selected from a simple Ge and an alloy containing Ge.
<3> The phase-change optical information recording medium according to <2>, wherein the Ge-containing alloy is GeTe or GeSb.
<4> The phase change optical information recording medium according to any one of <2> to <3>, wherein the content of the Ge simple substance and the Ge-containing alloy is 5 atomic% or less as the Ge simple substance.
In the phase change optical information recording medium according to any one of <2> to <4>, the storage life of the recording layer may be increased by including at least one of Ge alone and an alloy containing Ge. In addition, since a signal difference can be obtained even with a thin film thickness, a multilayer recording layer can be formed without reducing the recording linear velocity.

  <5> The above <1> to <4>, wherein the optical constant in the amorphous state of the recording layer is n = 2.7 to 3.1 and k = 1.5 to 3.0 at a blue wavelength (405 nm) Any one of the phase-change optical information recording media. In the phase change optical information recording medium described in <5>, a reflectance difference between marks recorded at a blue wavelength can be obtained, and excellent optical characteristics can be obtained even at a blue wavelength.

<6> On the substrate, at least a first recording layer and a second recording layer are stacked in this order, and the first recording layer located in front of the laser irradiation direction is In _α Te _β (where α, β represents a composition ratio (atomic%), 43.5 ≦ β ≦ 64 and α + β = 100), and the film thickness of the first recording layer is 4 to 12 nm. This is a phase change optical information recording medium. In the phase change type optical information recording medium of the present invention, the recording layer can be multilayered to increase the recording density together with the high-speed recording, and the first recording layer is made of an alloy containing at least In and Te as main components. As a result, it is possible to obtain a difference in reflectance between marks recorded at the blue wavelength, and to obtain excellent optical characteristics even at the blue wavelength.

<7> The second recording layer contains In _α Te _β (where α and β represent a composition ratio (atomic%), 43.5 ≦ β ≦ 64, and α + β = 100), The phase change optical information recording medium according to <6>, wherein the thickness of the second recording layer is 4 to 20 nm.
<8> The phase change optical information recording medium according to any one of <6> to <7>, wherein the film thickness of the first recording layer is smaller than the film thickness of the second recording layer.

<9> The phase according to any one of <6> to <8>, wherein at least one of the first recording layer and the second recording layer contains at least one selected from simple Ge and an alloy containing Ge. This is a change-type optical information recording medium.
<10> The phase-change optical information recording medium according to <9>, wherein the alloy containing Ge is GeTe or GeSb.
<11> The phase change optical information recording medium according to any one of <9> to <10>, wherein the content of the Ge simple substance and the Ge-containing alloy is 5 atomic% or less as the Ge simple substance.
In the phase change optical information recording medium according to any one of <9> to <11>, the storage life of the recording layer is increased by including at least one of Ge alone and an alloy containing Ge. Furthermore, since a signal difference can be obtained even with a thin film thickness, a multilayer recording layer can be formed without reducing the recording linear velocity.

<12> The phase change optical information recording medium according to any one of <6> to <11>, wherein the transmittance of the first recording layer at a recording / reproducing laser beam wavelength is 40 to 70%.
<13> On the substrate, at least a first lower dielectric layer, a first recording layer, a first upper dielectric layer, a first sulfide-resistant barrier layer, a first reflective layer, a transparent thermal diffusion layer, a first environmental protection layer, <6, in which an adhesive layer, a second environmental protection layer, a second lower dielectric layer, a second recording layer, a second upper dielectric layer, a second anti-sulfur barrier layer, and a second reflective layer are laminated in this order. > To <12>. The phase change optical information recording medium according to any one of <1> to <12>.
<14> The phase change optical information recording medium according to <13>, wherein the first reflective layer has a thickness of 20 nm or less.

  According to the present invention, conventional problems can be solved, a difference in reflectance between marks recorded at a blue wavelength can be obtained, an excellent optical characteristic can be obtained even at a blue wavelength, and a high recording density can be achieved. Thus, it is possible to provide a phase change optical information recording medium in which the recording sensitivity does not decrease even during high-speed recording. Further, according to the present invention, the recording layer can be multilayered in the thickness direction of the recording medium, and the recording density can be further increased along with the high-speed recording.

In the first embodiment, the phase change optical information recording medium of the present invention is formed by laminating at least a lower dielectric layer, a recording layer, an upper dielectric layer, a sulfide-resistant barrier layer, and a reflective layer in this order on a substrate. Further, it has other layers as required (hereinafter, it may be referred to as a single layer type optical information recording medium).
Specifically, as shown in FIG. 1, a lower dielectric layer 2, a recording layer 3, an upper dielectric layer 4, a sulfide-resistant barrier layer 5, and a reflective layer 6 are sequentially laminated on a transparent substrate 1. Further, in the present invention, the recording layer 3 is composed mainly of In _α Te _β (where α and β represent composition ratios (atomic%), 43.5 ≦ β ≦ 64, and α + β = 100). The film thickness of the recording layer is 4 to 20 nm, preferably 10 to 16 nm. The composition ratio (atomic%) of α and β is preferably 55 ≦ β ≦ 60 and α + β = 100.
If the film thickness of the recording layer 3 is less than 4 nm, a difference in reflectance due to an effective signal may not be obtained after recording. If the film thickness exceeds 20 nm, it is difficult to record because the heat capacity of the recording layer increases. In addition, the reproduction signal output may be reduced.

Since the recording layer 3 is made of an alloy containing at least In and Te as main components, it is possible to obtain a reflectance difference between marks recorded at a blue wavelength. A signal difference can be obtained even at a normal film thickness and even at a thinner film thickness. Specifically, the optical constants in the amorphous state of the recording film containing In and Te as main components are n = 2.7 to 3.1 and k = 1.5 to 3.0 at a blue wavelength (405 nm). . FIG. 4 shows an example of a change in optical characteristics depending on the wavelength of the optical information recording medium in which the recording layer 3 is composed of In ₍₅₀₎ Te ₍₅₀₎ .

Here, in FIG. 4, the display of amorphous n and amorphous k assumes an amorphous mark that has become amorphous by being rapidly cooled after being heated to a molten state by laser irradiation, and its optical constant n and extinction coefficient. The value of k is shown. The vertical axis indicating the value of the optical constant n is on the left side, and the vertical axis indicating the value of the extinction coefficient k is on the right axis. The values in FIG. 4 plot the measured values after film formation of the phase change recording material in an amorphous state. The indications of the crystal n and the crystal k indicate the values of the optical constant n and the extinction coefficient k of the phase change recording film that has been crystallized by heating to a molten state by laser irradiation and then gradually cooling. Actually, the membrane surface is initialized by the initialization device, and the measured values are plotted. For both the optical constant n and the extinction coefficient k, the amorphous state is indicated by a thick line, and the crystalline state is indicated by a thin line. Moreover, the arrow has shown the width | variety of the change from an amorphous state in a blue wavelength (405 nm) to a crystalline state. The larger the change width, the larger the signal difference between the unrecorded state and the recorded state. The optical constant difference of the In ₍₅₀₎ Te ₍₅₀₎ material at the blue wavelength is Δn = 1.53 and Δk = 0.594.

  The recording layer 3 preferably contains at least one of Ge and an alloy containing at least one of Ge so that the content of Ge is 5 atomic% or less in order to improve characteristics such as storage stability. With this configuration, the storage life of the recording layer can be extended. Further, since a signal difference can be obtained even with a thin film thickness, a multilayer recording layer can be formed without reducing the recording linear velocity.

  As the alloy containing Ge, GeTe or GeSb is preferable. In addition to improving the storage stability by including Ge, GeTe has an optical constant n at 405 nm of 3.06 and an extinction coefficient k of 1.6, which is the same optical characteristic as InTe. The function of InTe which is optically the main component is not impaired. In addition, in the case of GeSb, the storage stability can be improved by including Ge. In addition, the alloy of In and Sb generated when melted and mixed itself functions as a phase change recording layer, so that the recording linear velocity is not lowered.

  As the material of the substrate 1, glass, ceramics, resin, or the like is usually used, but a resin substrate is preferable in terms of moldability and cost. Examples of the resin include polycarbonate resin, acrylic resin, epoxy resin, polystyrene resin, acrylonitrile-styrene copolymer resin, polyethylene resin, polypropylene resin, silicone resin, fluorine resin, ABS resin, and urethane resin. A polycarbonate resin and an acrylic resin are preferable in terms of moldability, optical characteristics, and cost.

  The thickness of the substrate 1 is not particularly limited, and is determined by the wavelength of the laser that is normally used and the light collecting characteristics of the pickup lens. A substrate having a thickness of 1.2 mm is used for a CD system having a wavelength of 780 nm, and a substrate having a thickness of 0.6 mm is used for a DVD system having a wavelength of 650 to 665 nm. In addition, for optical discs using a 405 nm blue laser, the pickup lens has a numerical aperture (NA) of 0.6 mm (in the case of numerical aperture 0.65) and a cover of 0.1 mm to 1.1 mm, depending on the numerical aperture (NA). A layered layer (when the numerical aperture is 0.85) is preferable.

The lower dielectric layer 2 and the upper dielectric layer 4 have effects such as preventing deterioration and alteration of the recording layer 3, increasing the adhesive strength of the recording layer 3, and enhancing the recording characteristics. Metal oxides such as SiO ₂ , ZnO, SnO ₂ , Al ₂ O ₃ , TiO ₂ , In ₂ O ₃ , MgO, ZrO ₂ , nitrides such as Si ₃ N ₄ , AlN, TiN, BN, ZrN, ZnS, Examples thereof include sulfides such as In ₂ S ₃ and TaS ₄ , carbides such as SiC, TaC, B ₄ C, WC, TiC, and ZrC, diamond-like carbon, and mixtures thereof. These materials can be used alone or as a mixture. When heat resistance is required, the melting point must be higher than that of the recording layer.
The lower dielectric layer 2 and the upper dielectric layer 4 may be formed by various vapor deposition methods such as vacuum deposition, sputtering, plasma CVD, photo CVD, ion plating, electron beam deposition. The law is used. Among these, the sputtering method is excellent in mass productivity and film quality.
The thickness of the lower dielectric layer 2 and the upper dielectric layer 4 is not particularly limited and can be appropriately selected according to the purpose. Usually, the lower protective layer is preferably 50 to 80 nm, and the upper protective layer is 10 nm. ˜30 nm is preferred. It is determined by recording characteristics such as reflectance, recording power margin, jitter and signal stability of repeated recording, and quality characteristics such as high temperature and high humidity storage and heat cycle test.

The sulfide-resistant barrier layer 5 is preferably made of a material having an effect of preventing corrosion caused by sulfidation of the metal film used for the reflective layer. For example, a mixed layer of SiC and SiO ₂ , and the lower and upper dielectric layer materials Examples include various metal oxides, nitrides, carbides, or mixtures thereof.
The formation method of the sulfide-resistant barrier layer 5 is the same as that of the lower dielectric layer 2.
The thickness of the sulfurization resistant barrier layer 5 is usually 3 to 10 nm.

As the reflective layer 6, for example, a metal material such as Al, Au, Ag, Cu, Ta, or an alloy thereof can be used. Moreover, Cr, Ti, Si, Cu, Ag, Pd, Ta, etc. can be used as an additive element to these metal materials. Such a reflective layer 6 can be formed by various vapor deposition methods, for example, vacuum deposition, sputtering, plasma CVD, photo CVD, ion plating, electron beam deposition, and the like. Among these, the sputtering method is excellent in mass productivity and film quality.
The thickness of the reflective layer 6 is not particularly limited and can be appropriately selected according to the purpose. Usually, in the case of one-layer recording, 100 to 200 nm is preferable.

  The environmental protection layer 7 has an effect of protecting the thin film laminated structure of the optical information recording medium of the recording layer in the process and at the time of becoming a product, and is usually formed of an ultraviolet curable resin. The thickness of the environmental protection layer is preferably 2 to 5 μm.

  The adhesive layer 8 is used to bond the transparent substrate 1 on which an information signal is written and the dummy substrate 9, and is a double-sided adhesive sheet, a thermosetting resin, or an ultraviolet curable resin in which an adhesive is applied to both sides of the base film. To form. The thickness of the adhesive layer is usually about 50 μm.

  The dummy substrate 9 does not need to be transparent when an adhesive sheet or a thermosetting resin is used as an adhesive layer, but is a transparent substrate that transmits ultraviolet rays when an ultraviolet curable resin is used for the adhesive layer. The thickness of the substrate is usually 0.6 mm, which is the same as that of the transparent substrate 1 on which information signals are written.

In the second embodiment, the phase-change optical information recording medium of the present invention is formed by laminating at least a first recording layer and a second recording layer in this order on a substrate, and, if necessary, other layers. (Hereinafter sometimes referred to as a multilayer optical information recording medium). Thus, by increasing the number of recording layers in the thickness direction of the recording medium of the optical information recording medium, it is possible to increase the recording density as well as the high-speed recording.
In the optical information recording medium, the first recording layer located in front of the laser irradiation direction contains In _α Te _β (where 43.5 ≦ β ≦ 64 and α + β = 100), The film thickness of the first recording layer is 4 to 12 nm.

Specifically, as shown in FIG. 2, on the substrate 1 ′, at least a first lower dielectric layer 2 ′, a first recording layer 3 ′, a first upper dielectric layer 4 ′, and a first sulfur-resistant barrier layer. 5 ′, first reflective layer 6 ′, transparent thermal diffusion layer 10, first environmental protection layer 7 ′, adhesive layer 8 ′, second environmental protection layer 77, second lower dielectric layer 22, second recording layer 33, The second upper dielectric layer 44, the second anti-sulfur barrier layer 55, and the second reflective layer 66 are laminated in this order.
In this case, the substrate 1 ′, the first lower dielectric layer 2 ′, the first recording layer 3 ′, the first upper dielectric layer 4 ′, the first anti-sulfur barrier layer 5 ′, and the first reflective layer 6 ′ are This is the same as the substrate 1, the lower dielectric layer 2, the recording layer 3, the upper dielectric layer 4, the sulfide-resistant barrier layer, and the reflective layer 6 described above. The second lower dielectric layer 22 is the same as the first lower dielectric layer 2 ′, the second recording layer 33 is the same as the first recording layer 3 ′, and the second upper dielectric layer 44 is the first upper dielectric layer. Similar to the body layer 4 ′, the second sulfur-resistant barrier layer 55 is preferably configured similarly to the first sulfur-resistant barrier layer 5 ′, and the second reflective layer 66 is configured similarly to the first reflective layer 6 ′.

  The first recording layer 3 ′ is positioned in front of the laser irradiation direction and is formed to have a film thickness of 4 to 12 nm because the transmittance is increased by making the film thickness thinner than that of the second recording layer 33. To get. When the film thickness of the first recording layer 3 'is less than 4 nm, it is not possible to obtain a difference in reflectance due to an effective signal after recording. On the other hand, if the thickness exceeds 12 nm, the transmittance becomes low, and recording on the second recording layer becomes difficult. More preferable is 6 to 10 nm from the viewpoint of both recording and transmittance.

The transmittance of the first recording layer at the recording / reproducing laser beam wavelength (for example, blue wavelength (405 nm)) is preferably 40 to 70%, more preferably 45 to 60%.
When the transmittance is less than 40%, the sensitivity of the second recording layer is lowered, and it may not be possible to perform good recording and reproduction. When the transmittance is more than 70%, the sensitivity of the first recording layer is lowered. In some cases, recording and reproduction cannot be performed satisfactorily.
Here, the said transmittance | permeability can be measured in the transmittance | permeability measurement mode (RTA mode) of optical disk optical characteristic evaluation apparatus model: TETA-RT2 by Steag Etoptik GmbH, for example. More specifically, after measuring the spectrum of the standard sample, calibration is performed, and then the sample is measured, whereby the transmittance, absorption rate, and reflectance values can be measured.

  The configuration of the second recording layer 33 may be the same as that of the first recording layer 3 '. That is, a recording layer material made of an alloy containing at least In and Te as main components is used, and the film thickness is 4 to 20 nm. Further, it can be formed of a material different from that of the first recording layer, and examples thereof include SbTe, GeSbTe, GeTe, GeTeSn, InSb, and GaSb.

  When the optical information recording medium is multilayered, as shown in FIG. 2, the transparent thermal diffusion layer 10, the environmental protection layer 7 ′, the first adhesive layer 8 ′, and the second environmental protection layer are formed on the first reflective layer 6 ′. 77 is formed in order, and the lower dielectric layer 22 is preferably formed on the second environmental protection layer 77. In addition, it is preferable to form the dummy substrate 9 on the second reflective layer 66.

A transparent thermal diffusion layer 10 is provided between the first reflective layer 6 ′ and the first environmental protection layer 7 ′. In the case of an optical information recording medium having two recording layers, the thickness of the reflective layer 6 adjacent to the recording layer on the laser beam incident side needs to transmit light to the second recording layer 33, so that it is 20 nm or less. . However, this reflective layer also has a function of rapidly cooling the recording layer material in order to form an amorphous mark. However, it is necessary to prevent the function from deteriorating due to a decrease in film thickness. It is usually arranged as an alternative.
As the transparent thermal diffusion layer 10, SnO ₂ , In ₂ O ₃ used as a transparent conductive film, ITO (Indium Tin Oxide) which is a mixture of In ₂ O ₃ and SnO ₂ , ZnO, ZnO is doped with Al. ZnO: Al, IZO (Indium Zinc Oxide) which is a mixture of In ₂ O ₃ and ZnO is used. The thickness of the transparent heat diffusion layer is preferably 30 to 130 nm.
The first environmental protection layer 7 ′ and the first adhesive layer 8 ′ are set to have a film thickness so that the first recording layer and the second recording layer can be optically separated, and the normal use laser wavelength is 405 nm. In this case, the total of the first environmental protection layer 7 ′ and the first adhesive layer 8 ′ is about 30 μm. Further, the thickness of the reflective layer 66 of the second recording layer 33 on the back side is preferably 100 to 200 nm, which is the same as in the case of the single recording layer.

  Examples of the present invention will be described below, but the present invention is not limited to these examples.

(Example 1)
1 is formed as follows on a substrate made of polycarbonate resin 1 having a track pitch of 0.44 μm and a thickness of 0.6 mm and provided with irregularities on the surface to produce an optical disk (media). did. First, ZnS · SiO ₂ as the lower dielectric layer 2 was formed to a thickness of 50 nm using a single wafer sputtering apparatus. In ₄₃ Te ₅₇ as the recording layer 3 was formed on the lower dielectric layer so as to have a thickness of 16 nm. On the recording layer, the same ZnS · SiO ₂ as the lower dielectric layer 2 was formed as the upper dielectric layer 4 so as to have a thickness of 10 nm. A mixed layer of SiC and SiO ₂ (SiC 80 atom%: SiO ₂ 20 atom%) as a sulfur-resistant barrier layer 5 was formed on the upper dielectric layer so as to have a thickness of 4 nm. Finally, pure Ag as the reflective layer 6 was formed to have a thickness of 140 nm and taken out from the sputtering apparatus.
After completion of the sputtering film formation, an ultraviolet curable resin was spin-coated on the reflective layer, and then the ultraviolet protective resin was cured to form an environmental protection layer 7 having a thickness of 3 μm. Next, the optical information recording medium of Example 1 was produced by bonding the dummy substrate 9 having a thickness of 0.6 mm via the adhesive layer 8 (thickness 47 μm) on the environmental protection layer.

Next, using the phase change type optical disc initialization apparatus (POP120-3Ra manufactured by Hitachi Computer Co., Ltd.), the optical information recording medium was laser-initialized with a processing time of about 100 seconds under the following conditions.
The recording medium is rotated by CLV (Constant Linear Velocity) recording, the linear velocity is 9.0 m / s, the feed amount is 36 μm / rotation, the initialization range is a radial position of 23 to 58 mm, and the laser power is 1400 mW. It was. The center emission wavelength of the LD of this apparatus is 810 ± 10 nm, and the spot size is about 1 μm × 96 ± 5 μm.

  Next, evaluation was performed using an optical disk evaluation apparatus (PDUSTEC, DDU1000) having a pickup with a numerical aperture NA (Numerical Aperture) 0.65 mounted with a 405 nm semiconductor laser. The recording density is 0.17 μm / bit, and the recording linear velocity is 6.5 m / s. The conditions of the evaluation power were Pw = 10-14 mW, Pe = 5 mW, reading power Pr = 0.5 mW, and an optimized pulse strategy. The evaluation results are shown in Table 1. From the results of Table 1, in the optical information recording medium of Example 1, a jitter of 9% or less and a modulation of 60% or more due to the optical random pattern were obtained.

  Next, this optical information recording medium was put into a storage test tank. It was stored in a high-temperature and high-humidity bath at 80 ° C.-RH 85% for 100 hours, and changes in jitter and modulation were observed again. The change in jitter was 0.3% and the change in modulation was 2%. The evaluation results are shown in Table 1.

(Example 2)
An optical information recording medium of Example 2 was produced in the same manner as in Example 1 except that (In ₄₃ Te ₅₇ ) ₆₇ (Ge ₁₅ Te ₈₅ ) ₃₃ was used for the recording layer 3 in Example 1.
Next, evaluation was performed by a pulse strategy optimized in the same manner as in Example 1. The evaluation results are shown in Table 1. From the results in Table 1, a jitter of 9% or less and a modulation of 60% or more due to a random pattern were obtained.

  Next, this optical information recording medium was put into a storage test tank. It was stored in a high-temperature and high-humidity bath at 80 ° C.-RH 85% for 300 hours, and changes in jitter and modulation were observed again. The change in jitter was 0.3% and the change in modulation was 2%. The evaluation results are shown in Table 1.

(Example 3)
The optical information recording medium of Example 3 was obtained in the same manner as in Example 1 except that (In ₄₃ Te ₅₇ ) ₇₉ (Ge _14.5 Sb _85.5 ) ₂₁ was used for the recording layer 3 in Example 1. Produced.
Next, evaluation was performed by a pulse strategy optimized in the same manner as in Example 1. The evaluation results are shown in Table 1. From the results in Table 1, a jitter of 9% or less and a modulation of 60% or more due to a random pattern were obtained.

  Next, this recording medium was put into a storage test tank. It was stored in a high-temperature and high-humidity bath at 80 ° C.-RH 85% for 300 hours, and changes in jitter and modulation were observed again. The change in jitter was 0.3% and the change in modulation was 2%. The evaluation results are shown in Table 1.

Example 4
As shown in FIG. 2, each layer was formed as follows on a polycarbonate resin substrate having a track pitch of 0.44 μm and a surface with irregularities and a thickness of 0.6 mm, thereby producing an optical information recording medium. .
First, ZnS · SiO ₂ (SiO ₂ 20 atomic%) as the first lower dielectric layer 2 ′ was formed to a thickness of 50 nm using a single wafer sputtering apparatus. In ₄₃ Te ₅₇ as the first recording layer 3 ′ was formed on the first lower dielectric layer so as to have a thickness of 6 nm. On the first recording layer, the same ZnS · SiO ₂ as the first lower dielectric layer 2 ′ was formed as the first upper dielectric layer 4 ′ so as to have a thickness of 10 nm. A mixed layer of SiC and SiO ₂ (SiC 80 atom%: SiO ₂ 20 atom%) as the _first sulfur-resistant barrier layer 5 ′ was formed on the first upper dielectric layer so as to have a thickness of 4 nm. On the first sulfidation-resistant barrier layer, Ag as the first reflective film 6 ′ was formed to a thickness of 10 nm. On the first reflective film, IZO (In ₂ O ₃ mixed with 5 atomic% of ZnO) as the transparent thermal expansion layer 10 was formed to a thickness of 80 nm. Next, the first environmental protection layer 7 ′ was formed using an ultraviolet curable resin so as to have a thickness of 3 to 5 μm.
Note that only the first recording layer alone is separately formed on the surface of the same polycarbonate substrate on which the track is not formed, and the transmittance of an optical disk optical characteristic evaluation apparatus (Steag Etoptik GmbH, model: ETA-RT2). When the transmittance was measured in the measurement mode (RTA mode), a sufficient transmittance of 50% was obtained at a wavelength of 405 nm.

Next, a substrate in which the second information layer to be a pair for bonding was formed in a reverse film formation configuration was manufactured.
First, using a single wafer sputtering apparatus, Ag as the second reflective layer 66 was formed to a thickness of 140 nm. A mixed layer of SiC and SiO ₂ (SiC 80 atom% · SiO ₂ 20 atom%) as the _second sulfur-resistant barrier layer 55 was formed on the second reflective layer so as to have a thickness of 5 nm. On the second anti-sulfur barrier layer, ZnS · SiO ₂ as the second upper dielectric layer 44 was formed to a thickness of 12 nm. A Ge ₅ Sb ₇₅ Te ₂₀ film as the second recording layer 33 was formed on the second upper dielectric layer so as to have a thickness of 15 nm. On the second recording layer, ZnS · SiO ₂ as the second lower dielectric layer 22 is formed so as to have a thickness of 50 nm. Finally, an ultraviolet curable resin is applied and cured, and the second environmental protection layer 77 is formed. The thickness was 3 to 5 μm.
Next, the substrate on which the first recording layer was formed and the substrate on which the second recording layer was formed were bonded via an adhesive layer 8 ′ to form a two-layer optical information recording medium. The thickness of the adhesive layer 8 was adjusted while measuring the thickness so that the total thickness of the environmental protection layers 7 and 77 and the adhesive layer 8 was about 35 ± 5 μm.

  Next, the disk characteristics were evaluated by initializing with a large-diameter laser initializing apparatus while aligning the furcas one layer at a time. The evaluation results are shown in Table 1. The semiconductor laser power conditions used for evaluation at this time were the first recording layer recording conditions Pw = 10 to 14 mW, Pe = 5 mW, and reading power Pr = 0.8 to 1.2 mW. Furthermore, the recording conditions of the second recording layer were Pw = 10-14 mW, Pe = 5 mW, and reading power Pr = 0.5-1.2 mW.

  Next, this optical information recording medium was put into a storage test tank. It was stored in a high-temperature and high-humidity bath at 80 ° C.-RH 85% for 300 hours, and changes in jitter and modulation were observed again. The change in jitter was 0.3% and the change in modulation was 2%. The evaluation results are shown in Table 1.

(Example 5)
In Example 4, two layers were formed in the same manner as in Example 4 except that the first recording layer was changed to 6 nm in thickness consisting of In ₄₃ Te ₅₇ and the second recording layer was changed to 16 nm in thickness consisting of In ₄₃ Te _57. Type optical information recording medium was produced.
The obtained two-layer optical information recording medium was evaluated in the same manner as in Example 4. The results are shown in Table 1.

(Example 6)
In Example 1, an optical information recording medium was produced in the same manner as in Example 1 except that the film thickness of the recording layer was 4 nm.
The obtained optical information recording medium was evaluated in the same manner as in Example 4. The results are shown in Table 1. Although the recording power was increased by 1 mW, recording was possible at the same recording linear velocity.

(Example 7)
In Example 1, an optical information recording medium was produced in the same manner as in Example 1 except that the film thickness of the recording layer was 6 nm.
The recording characteristics of the obtained optical information recording medium were measured by optimizing the recording strategy. The results are shown in Table 1.

(Example 8)
In Example 1, an optical information recording medium was produced in the same manner as in Example 1 except that the thickness of the recording layer was 10 nm.
The recording characteristics of the obtained optical information recording medium were measured by optimizing the recording strategy. The results are shown in Table 1.

Example 9
An optical information recording medium was manufactured in the same manner as in Example 1 except that the composition of the recording layer was In ₅₀ Te ₅₀ and the thickness of the recording layer was 10 nm.
The recording characteristics of the obtained optical information recording medium were measured by optimizing the recording strategy. The results are shown in Table 1.

(Example 10)
An optical information recording medium was produced in the same manner as in Example 1, except that the composition of the recording layer was In ₄₀ Te ₆₀ and the thickness of the recording layer was 10 nm.
The recording characteristics of the obtained optical information recording medium were measured by optimizing the recording strategy. The results are shown in Table 1.

  In Examples 9 and 10, the results shown in Table 1 were within a range that can be normally used as an optical information recording medium except that the recording power was increased by several mW. As for the storage characteristics, the change in 300H jitter under the condition of 80 ° C.-85% RH was 0.5% in jitter change and 1% in modulation, and there was no problem with the change with time.

(Comparative Example 1)
First, as a preliminary experiment, a recording layer having a film thickness of 6 to 18 nm was manufactured with the configuration of FIG. 1 in steps of 2 nm, and the recording linear velocity was measured. At 6 nm and 8 nm, the recording linear velocities were 3.5 m / s and 5 m / s. On the contrary, at 12 m / s or more on the thick side, the same recording linear velocity 6.5 m / s as 10 nm was measured. Therefore, 10 nm was selected as the film thickness corresponding to 6.5 m / s. Based on this result, we entered this experiment.
First, on the polycarbonate resin substrate 1 having a track pitch of 0.44 μm and a thickness of 0.6 mm and having an uneven surface, a layer similar to that shown in FIG. 2 is formed as follows. Was made. First, ZnS.SiO ₂ (SiO ₂ 20 atomic%) as the first lower dielectric layer 2 ′ was formed to a thickness of 50 nm using a single wafer sputtering apparatus. On the first lower dielectric layer, (Ag ₂ In ₃ Sb ₇₀ Te ₂₅ ) 85 (Ge ₃₀ Se ₇₀ ) ₁₅ as a first recording layer 3 ′ was formed to a thickness of 10 nm. On the first recording layer, the same ZnS · SiO ₂ as the first lower dielectric layer 2 ′ was formed to have a thickness of 12 nm as the first upper dielectric layer 4 ′. A mixed layer of SiC and SiO ₂ (SiC 80 atom%: SiO ₂ 20 atom%) as the _first sulfur-resistant barrier layer 5 ′ was formed on the first upper dielectric layer so as to have a thickness of 4 nm. On the first sulfidation-resistant barrier layer, Ag of the first reflective film 6 ′ was formed to a thickness of 10 nm. After forming IZO (mixed with 5 atomic% of ZnO in In ₂ O ₃₎ as a transparent thermal expansion layer 10 on the first reflective film so as to have a thickness of 80 nm, the first environmental protection layer 7 ′ is made of ultraviolet rays. It formed so that thickness might be set to 3-5 micrometers using hardening resin.

Next, a substrate on which a substrate having a second recording layer to be a pair for bonding was formed in a reverse film formation configuration was manufactured. Specifically, the light of Comparative Example 1 having the same layer configuration as that of FIG. 2 is used under the same conditions as in Example 4 except that the second recording layer 33 is Ag ₂ In ₃ Sb ₇₀ Te ₂₅ (thickness 16 nm). An information recording medium was produced.

  The recording / reproduction characteristics (jitter minimum recording sensitivity of the first recording layer and the second recording layer) of the media of Example 4 and the media of Comparative Example 1 were evaluated. The evaluation conditions were laser wavelength: 405 nm, numerical aperture NA of the objective lens of the optical system: 0.65, rotational linear velocity of the disk: 6.5 m / s, and recording linear density: 0.17 μm / bit. As a result of the evaluation, in Comparative Example 1, recording was possible with a laser output 1 mW higher than the jitter minimum recording sensitivity of the first recording layer and the second recording layer of Example 1. The evaluation results are shown in Table 1.

  Next, this recording medium was put into a storage test tank. It was stored in a high-temperature and high-humidity tank at 80 ° C. and RH 85% for 300 hours, and changes in jitter and modulation were observed again. The change in jitter was 0.3% and the change in modulation was 2%. The evaluation results are shown in Table 1.

(Comparative Example 2)
In Comparative Example 1, Ge _20.8 Sn ₁₀ Sb _15.4 Te _53.8 was used as the first recording layer material, and GeN was stacked on the top and bottom of the first recording layer so as to have a thickness of 3 nm. In order to match these, only the first recording layer side substrate was formed in the same manner as in Comparative Example 1 except that the thickness of the first lower protective layer was increased to 60 nm. Furthermore, an optical disk of Comparative Example 2 was manufactured by bonding a 0.6 mm-thick dummy substrate that was not formed through an adhesive layer.

  Since the material system is different, the evaluation power was reviewed and the evaluation was performed under the measurement conditions of Pw = 10 mW, Pe = 5 mW (3 m / s), Pb = 0.1 mW, and Pr = 0.8 mW. When the recording strategy was optimized and evaluated, the recording sensitivity was good and recording was possible at 10 mW, but the recording linear velocity was 3 m / s, and when the linear velocity was increased to 6.5 m / s, the jitter deteriorated and modulation was performed. Could not be measured. The evaluation results are shown in Table 1.

(Comparative Example 3)
In Example 4, an optical information recording medium of Comparative Example 3 was produced in the same manner as in Example 4 except that the thickness of the first recording layer was 3 nm.
Only the first recording layer alone is separately formed, and is separately formed on the surface of the same polycarbonate substrate on which the track is not formed. When the transmittance was measured in the transmittance measurement mode (RTA mode), a transmittance as high as 75% was obtained at a wavelength of 405 nm.
When the first recording layer was evaluated, the jitter value was measured to be 20% as a display, but a clean eye pattern for a signal having a length of 3T to 14T was not obtained, and the modulation could not be measured. The second recording layer was measured to obtain a jitter of 8.9% and a modulation of 61%. The evaluation results are shown in Table 1.

(Comparative Example 4)
In Example 4, the optical information recording medium of Comparative Example 4 was produced in the same manner as in Example 4 except that the thickness of the first recording layer was 25 nm.
Only the first recording layer alone is separately formed and separately formed on the surface of the same polycarbonate resin substrate on which the track is not formed, and the optical disk optical property evaluation apparatus model: ETA-RT2 manufactured by Steag Etaoptik GmbH When the transmittance was measured in the rate measurement mode (RTA mode), a transmittance of 35% was obtained at a wavelength of 405 nm.
When the first recording layer was evaluated, the jitter value was 7.9% and the modulation was 63%. However, the second recording layer was measured and found to have a jitter of 18% and a modulation of 40%. The evaluation results are shown in Table 1.

(Comparative Example 5)
An optical information recording medium was fabricated in the same manner as in Example 1 except that the composition of the recording layer was In ₅₈ Te ₄₂ and the film thickness of the recording layer was 10 nm.
The recording characteristics of the obtained optical information recording medium were measured by optimizing the recording strategy. The results are shown in Table 1.

(Comparative Example 6)
An optical information recording medium was manufactured in the same manner as in Example 1 except that the composition of the recording layer was In ₃₅ Te ₆₅ and the film thickness of the recording layer was 10 nm.
The recording characteristics of the obtained optical information recording medium were measured by optimizing the recording strategy. The results are shown in Table 1.

  The phase-change optical information recording medium of the present invention has excellent recording characteristics especially at a blue wavelength (405 nm) and is widely used for CD-R, CD-RW, DVD + RW, DVD-RW, DVD-RAM, and the like. Can do.

FIG. 1 is an explanatory diagram showing an example of the layer structure of the optical information recording medium of the present invention. FIG. 2 is an explanatory view showing another example of the layer structure of the optical information recording medium of the present invention. FIG. 3 is a drawing showing an example of a change in optical characteristics depending on the wavelength of an optical information recording medium made of SbTe having a composition near the eutectic system (Sb ₇₅ Te ₂₅ ). FIG. 4 is a drawing showing an example of a change in optical characteristics depending on the wavelength of an optical information recording medium having a recording layer made of InTe.

Explanation of symbols

1, 1 'transparent substrate 2, 2' lower dielectric layer, first lower dielectric layer 3, 3 'recording layer 4, 4' upper dielectric layer, first upper dielectric layer 5, 5 'reflective layer anti-sulfurization Barrier layer, first reflective layer Sulfur-resistant barrier layer 6, 6 'Reflective layer 7, 7' Environmental protective layer, first environmental protective layer 8 Adhesive layer 9, 9 'Second transparent substrate (bonded substrate)
DESCRIPTION OF SYMBOLS 10 Transmission heat diffusion layer 22 2nd lower dielectric layer 44 2nd upper dielectric layer 55 2nd reflection layer Sulfur-resistant barrier layer 66 2nd reflection layer 77 Environmental protection layer

Claims (14)

On the substrate, at least a lower dielectric layer, a recording layer, an upper dielectric layer, a sulfide-resistant barrier layer, and a reflective layer are laminated in this order, and the recording layer is composed of In _α Te _β (where α and β are compositions). A phase change type characterized by containing a ratio (atomic%), 43.5 ≦ β ≦ 64, and α + β = 100), and a film thickness of the recording layer of 4 to 20 nm Optical information recording medium.   The phase change optical information recording medium according to claim 1, wherein the recording layer contains at least one selected from a simple Ge and an alloy containing Ge.   The phase change optical information recording medium according to claim 2, wherein the Ge-containing alloy is GeTe or GeSb.   The phase change optical information recording medium according to any one of claims 2 to 3, wherein the content of the Ge simple substance and the alloy containing Ge is 5 atomic% or less as the Ge simple substance.   5. The phase according to claim 1, wherein the optical constant in the amorphous state of the recording layer is n = 2.7 to 3.1 and k = 1.5 to 3.0 at a blue wavelength (405 nm). Changeable optical information recording medium. On the substrate, at least a first recording layer and a second recording layer are laminated in this order, and the first recording layer located in front of the laser irradiation direction is In _α Te _β (where α and β are the compositions) A phase change characterized by containing a ratio (atomic%), 43.5 ≦ β ≦ 64 and α + β = 100), and the thickness of the first recording layer being 4 to 12 nm Type optical information recording medium. The second recording layer contains In _α Te _β (where α and β represent a composition ratio (atomic%), 43.5 ≦ β ≦ 64, and α + β = 100). The phase change optical information recording medium according to claim 6, wherein the recording layer has a thickness of 4 to 20 nm.   8. The phase change optical information recording medium according to claim 6, wherein the first recording layer is formed thinner than the second recording layer.   9. The phase change optical information recording medium according to claim 6, wherein at least one of the first recording layer and the second recording layer contains at least one selected from Ge simple substance and an alloy containing Ge. .   The phase change optical information recording medium according to claim 9, wherein the Ge-containing alloy is GeTe or GeSb.   The phase change optical information recording medium according to any one of claims 9 to 10, wherein the content of the Ge simple substance and the Ge-containing alloy is 5 atomic% or less as the Ge simple substance.   The phase change optical information recording medium according to any one of claims 6 to 11, wherein the transmittance of the first recording layer at a recording / reproducing laser beam wavelength is 40 to 70%.   On the substrate, at least a first lower dielectric layer, a first recording layer, a first upper dielectric layer, a first anti-sulfur barrier layer, a first reflective layer, a transparent thermal diffusion layer, a first environmental protection layer, an adhesive layer, The second environmental protection layer, the second lower dielectric layer, the second recording layer, the second upper dielectric layer, the second anti-sulfur barrier layer, and the second reflective layer are laminated in this order. Any one of the phase change optical information recording media. The phase change optical information recording medium according to claim 13, wherein the thickness of the first reflective layer is 20 nm or less.

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